Yunan Prawoto

South Ural State University, Mechanic, Faculty Member

Universitas Siswa Bangsa Internasional, Mechanical Engineering, Faculty Member

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$Research paper thumbnail of Review of classical fracture mechanics and its application in fatigue cracking in residual stressed area$

Review of classical fracture mechanics and its application in fatigue cracking in residual stressed area

Fracture Mechanics Approach to Splitting in Low Spring Index Cold Coiling Process

Journal of Failure Analysis and Prevention, May 17, 2019

This paper is an attempt to understand the coil splitting phenomena by means of fracture mechanic... more This paper is an attempt to understand the coil splitting phenomena by means of fracture mechanics. The methods used combine the residual stress measurement with neutron and finite element analysis. The support of the metallurgical evaluation is used as evidence to justify the use of the fracture mechanics concept. Comparing coil springs manufactured at two different manufacturing lines, namely N1 and N6, residual stress distributions in three main directions were measured using neutron diffraction. The results of the residual stress measurement were then converted into the stress intensity factor to enable the analysis in fracture mechanics. The mixed-mode analysis of opening, Mode I, and in-plane shearing, Mode II, is used to solve the splitting problem. The discrepancy between the coil made at N1 and N6 was identified and taken into account in terms of the profile difference. Based on this difference, an FEA simulation was conducted. The results support the experimental finding, which is that the shape of the coil manufactured influences the pattern of the residual stress, which leads to different splitting behaviors. This simple analysis helps practitioners understand why, and how, some cold coiled products split after manufacturing. It is concluded that this very basic concept of fracture mechanics can be used to establish the limit of the cold coiling process by evaluation of the mixed-mode stress intensity factor to the fracture toughness of the material.

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Two-dimensional modeling to compute plastic zone in front of compact tension sample of a multiphase material

Computational Materials Science, Dec 1, 2009

More and more components subjected to dynamic high stress loading are heat treated to get multiph... more More and more components subjected to dynamic high stress loading are heat treated to get multiphase microstructure as their final products, instead of conventional tempered martensite. It is gaining popularity due its manufacturing benefits, including the elimination of the tempering process, and its better fatigue performance. Multiphase of ferrite and martensite benefits its fatigue performance by its high toughness yet maintains the high tensile properties due to controlled microstructure. The plastic zone size in front of the ...

Synergy of erosion and galvanic effects of dissimilar steel welding: Field failure analysis case study and laboratory test results

Journal of King Saud University: Engineering Sciences, 2013

Welding austenitic stainless steels to carbon and low alloy steels are widely practiced in the pr... more Welding austenitic stainless steels to carbon and low alloy steels are widely practiced in the process and construction industries. Their potential failures are underrated and underreported. In this research, erosion accelerated corrosion of a carbon steel-stainless steel galvanic couple was simulated to mimic the field failure analysis. The weight-loss of a metal during erosion-corrosion is caused by both galvanic corrosion component and erosion component. Furthermore, the results show that the percentage of corrosive weight-loss of the total weight-loss increases with the increasing cathode/anode area ratio, indicating the accelerating corrosion of carbon steel under the large cathode-small anode geometry.

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Re-visiting the ‘rule of mixture’ used in materials with multiple constituting phases: A technical note on morphological considerations in austenite case study

Computational Materials Science, Dec 1, 2012

This is a technical note highlighting a method on how to perform averaging the elastic properties... more This is a technical note highlighting a method on how to perform averaging the elastic properties. The drawback of the traditional rule of mixture (ROM) is briefly discussed. The technique considers the effect of morphology based on classical continuum mechanics, taking the advantages of fracture mechanics. As an example, a model that simulates the possible configuration of constituting phases commonly found in austenite microstructure is chosen. The result is compared with traditional ROM. It is found that although similar, the result is better due to the stress amplification that is accommodated in the method, unlike the traditional ROM, which merely considers only the volumetric ratio.

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$Research paper thumbnail of How to compute plastic zones of heterogeneous materials: A simple approach using classical continuum and fracture mechanics$

How to compute plastic zones of heterogeneous materials: A simple approach using classical continuum and fracture mechanics

International Journal of Solids and Structures, Aug 1, 2012

This is a short technical paper on how to use classical continuum and fracture mechanics to calcu... more This is a short technical paper on how to use classical continuum and fracture mechanics to calculate the plastic zones caused by cracks on heterogeneous or composite materials. As an example, a sample consisting of an a-phase and b-phase is used. A crack is introduced to the sample, and stress is then applied. The plastic zone in front of the crack resulting from the applied stress is then calculated using commercial software. The concept uses two-level modeling: a global model using homogenized stiffness from a unit cell of heterogeneous material and a local model for the a-phase and b-phase. While this paper is written for general purposes, a concrete example using ferrite and martensite is also presented along with the experimental data. General agreement between the model and the experiment is observed. This method eliminates the need for a cumbersome analytical approach.

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Failure Analysis and Life Assessment of Coating: The Use of Mixed Mode Stress Intensity Factors in Coating and Other Surface Engineering Life Assessment

Journal of Failure Analysis and Prevention, Dec 8, 2011

Unlike metals, where failure analysis and life assessment methods are quite established, the fail... more Unlike metals, where failure analysis and life assessment methods are quite established, the failure analysis and life assessment of coatings are often underrated and disregarded. This research encourages failure analysts to realize and avail the opportunity provided by an alternative approach. The authors use energy density mechanics concepts to develop a new parameter in coating blistering. A mixed mode stress intensity factor is used as a basis for the derivation. This new parameter will be useful for the researchers and practitioners engaged in coating life assessment. It is recommended that the assessor combines field-determined adhesion strength values and blister evaluation, together with laboratory-derived strain energy density data, to quantitatively predict remaining coating life. This approach also provides a tool in failure analysis.

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$Research paper thumbnail of Influence of ferrite fraction within martensite matrix on fatigue crack propagation: An experimental verification with dual phase steel$

Influence of ferrite fraction within martensite matrix on fatigue crack propagation: An experimental verification with dual phase steel

Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, Aug 1, 2012

The influence of a ferrite areal fraction within a martensite matrix on fatigue crack propagation... more The influence of a ferrite areal fraction within a martensite matrix on fatigue crack propagation is studied experimentally. The variation of the areal fraction is achieved by means of intercritical thermal treatment, which specifically aims at optimizing the resistance to fatigue loading. Within the intercritical annealing temperature range, the areal fraction of ferrite increases with decreasing soaking temperature. Furthermore, the experiment also reveals that the highest fatigue strength was achieved when the ferrite areal fraction was approximately 65%, which in this particular test, corresponds to 748 degrees C. It is concluded that appropriate thermal treatment can contribute to a significant improvement of fatigue properties and strength, which was also verified by computational modeling.

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$Research paper thumbnail of Interfacial fracture of the fibre-metal laminates based on fibre reinforced thermoplastics$

Interfacial fracture of the fibre-metal laminates based on fibre reinforced thermoplastics

Materials in engineering, Feb 1, 2015

ABSTRACT As the adhesion quality plays an important role in determining the mechanical performanc... more ABSTRACT As the adhesion quality plays an important role in determining the mechanical performance and environmental stability of most types of fibre-metal laminates (FMLs), investigating the interfacial fracture properties becomes one of the key factors for the improvement. Adhesion of a self-reinforced polypropylene (SRPP) and glass fibre reinforced polypropylene (GFPP) based FML is evaluated experimentally. Single Cantilever Beam (SCB) tests were performed to access interfacial fracture energy (Gc) of the bi-material laminates and their associated interlayer materials. Simulations mimicking the experiments were also performed. The energy needed to fracture was obtained experimentally and also via stress intensity factor from the simulations. The test results show that good adhesion between the aluminium and fibre reinforced thermoplastics can be achieved using a sulphuric acid anodising surface pre-treatment. Further examination has shown that the edges of the test samples highlighted the presence of significant fibre bridging in the SRPP and plastics deformation in the GFPP.

Linear Elastic Fracture Mechanics (LEFM) Analysis of the Effect of Residual Stress on Fatigue Crack Propagation Rate

Practical failure analysis, Oct 1, 2002

In this research, both residual and applied stresses are converted to stress intensity factors in... more In this research, both residual and applied stresses are converted to stress intensity factors independently and combined using the superposition principle. The fatigue crack propagation rates are predicted. Experiments using two different loading modes, constant applied stress intensity factor (SIF) range, and constant applied load modes are done for samples with and without initial tensile residual stresses. The samples with initial tensile residual stresses exhibit accelerations of the crack propagation rates. The results show that the weight function method combined with the three-component model provides a good prediction of fatigue crack propagation rates in tensile residual stress fields.

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Effect of Prior Austenite Grain Size on the Morphology and Mechanical Properties of Martensite in Medium Carbon Steel

Journal of Materials Science & Technology, May 1, 2012

In industrial application, unintentional manufacturing line troubles often consequence in heating... more In industrial application, unintentional manufacturing line troubles often consequence in heating raw materials excessively, in terms of either time or temperature. One of the effects of such occurrence is a product with a variation of prior austenite grain size, even if after the heat treatment the end result is the same, martensite. The variation of the prior austenite grain size is believed to vary the end results of the martensite. This undesirable variation includes the variation of fatigue resistance, impact strength, yield strength, hardness, etc. This research studies the effect of the prior austenite grain size on the morphology of the martensite microstructure. The results show that within the typical industrial application of temperature and holding time set up, as holding time or the temperature increases, the prior austenite average diameter increases. The block and packet sizes in the martensite also increase. The variation of mechanical property dependence on the grain size is indeed due to the different characteristics reflected in the martensite morphology. With respect to the same area, smaller grain has more blocks and packets, which agrees with higher dislocation density verified with transmission electron microscopic evaluation.

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On the Influence of the Initial Shear Damage to the Cyclic Deformation and Damage Mechanism

Metals, Jun 23, 2022

This article is an open access article distributed under the terms and conditions of the Creative... more

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Quasi Tri‐Axial Method for the Fabrication of Optimized Polyurethane Auxetic Foams

Physica Status Solidi B-basic Solid State Physics, May 28, 2019

This paper describes the fabrication of polymeric auxetic foam using a quasi tri-axial compressio... more This paper describes the fabrication of polymeric auxetic foam using a quasi tri-axial compression method. In this method, the conversion process is executed by applying a quasi tri-axial compression on conventional closedcell polyurethane foams. In order to achieve optimum auxetic characteristics, the densification points in various directions are evaluated. In addition, the heating time of the compressed foam is also determined and applied to minimize the residual stress due to the volumetric compression. It leads to the fabrication of auxetic foams with achievable maximum re-entrancy and minimum collapsed cells without surface creasing. The results also show that the optimized auxetic foam exhibits isotropic behavior compared to its precursor foam as verified by the morphological analysis. The produced foam has all the desired properties of auxetic foams. The auxetic foam with a negative Poisson's ratio may have a great potential as the supplementary materials in energy absorption and structural applications.

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Carbon Restoration for Decarburized Layer in Spring Steel

Journal of Materials Engineering and Performance, Oct 1, 2004

It is well known that decarburization has a bad effect on spring steel strength. This research pr... more It is well known that decarburization has a bad effect on spring steel strength. This research presents a method to improve the product quality by means of recovering the decarburization layer. Unlike conventional methods, which usually use mechanical means, this method relies on a basic metallurgical principle, the process of diffusion. A carbon-rich layer is coated on the surface of the object. The object is then heat treated at conditions similar to the manufacturing process. To accomplish the objective, an experiment and a finite-element analysis (FEA) simulation were performed. The material chosen was a hypo-eutectoid steel with an excessive decarburization layer. The simulation was performed by digitizing the optical micrograph of decarburized raw materials and meshing the picture to get elements to start the analysis. Simple diffusion theory was then applied to the model. Various time parameters were used to simulate the redistribution of the carbon atoms. Comparable with the simulation, an experiment was also performed. The experiment began by coating a carbon-rich material onto decarburized raw material. The samples were then austenitized and subsequently either annealed or quenched. The state of the carbon restoration was then evaluated. The research concluded that the idea of carbon restoration can be implemented in the manufacturing process.

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Seeing auxetic materials from the mechanics point of view: A structural review on the negative Poisson’s ratio

Computational Materials Science, Jun 1, 2012

This paper summarizes research work related to materials with zero, or negative Poisson&amp;a... more This paper summarizes research work related to materials with zero, or negative Poisson&amp;amp;amp;amp;amp;#x27;s ratio, materials which are also referred to as auxetic materials. This review puts an emphasis on computations and aspects of their mechanics. It also considers diverse examples: from large structural, to biomedical applications. It is concluded that auxetic materials are technologically and theoretically important. While the development of the research has been dominated by periodic/ordered microstructures, the author predicts that future research ...

Critical view on the usage of C-ring specimen for stress corrosion crack (SCC) test on orthopedic implant: Experimental, numerical and analytical approaches

Materials Science and Engineering: C, Jul 1, 2012

As the failures of orthopedic devices due to stress corrosion cracking (SCC) have become more fre... more As the failures of orthopedic devices due to stress corrosion cracking (SCC) have become more frequent nowadays, research on this area also has become popular. Many published articles show the basic characterizations and evaluations of the SCC performed based on ASTM standards by using the C-ring sample. This paper discusses stress redistribution during SCC testing. The results show that the stress versus displacement equation presented in the standard is erroneous as the specimen begins to crack. It is only true for a non-cracked specimen. As the crack propagates, the sharpness of the crack tip minimizes the validity of the equation, even when the thickness reduction is taken into account.

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Stress Intensity Factor and Plastic Zone of Auxetic Materials: A Fracture Mechanics Approach to a Chiral Structure Having Negative Poisson’s Ratio

Mechanics of Advanced Materials and Structures, Oct 28, 2014

This article summarizes the method of analytical formulation and computational approach of stress... more This article summarizes the method of analytical formulation and computational approach of stress intensity factor and plastic zone calculation for auxetic materials, which have negative Poissons ratio. A chiral structurebased material is selected as an object of the study due to its popularity. The stress intensity factor is used in combination with the von Mises yielding condition to estimate the plastic zones shape and size. The results show that macroscopically the shape of the plastic zone for auxetic material is the same with that of ordinary materials. However, its size is smaller due to the reduction in its Youngs modulus from the solid material of which the auxetic material is made. Microscopically, an auxetic material has its plastic zone shape that is unique to its microstructure. Homogenization theory was convenient to use to bridge between the microscopic and macroscopic models.

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$Research paper thumbnail of Designing steel microstructure based on fracture mechanics approach$

Designing steel microstructure based on fracture mechanics approach

Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, May 1, 2009

Conventionally steel components subjected to high stress fatigue are heat treated by means of que... more Conventionally steel components subjected to high stress fatigue are heat treated by means of quenching and tempering. This method is popular due to both its convenience to implement and the fact that tempered martensite is good for both LCF (low cycle fatigue) and HCF (high cycle fatigue) areas. In LCF area, most of the life to failure is spent in crack initiation in un-cracked bodies. Under HCF loading conditions (where stress levels are far below the elastic limit), the life to failure is spent not only in crack initiation in un-cracked ...

Quantitative Fracture Mechanics Approach to Fatigue Life Improvement by Shot Peening Application

International journal of metallurgy and metal physics, Jun 30, 2020

Stress intensity factor has been a favorite tool in fracture mechanics due to its simplicity. Her... more Stress intensity factor has been a favorite tool in fracture mechanics due to its simplicity. Here, it is used to study the influence of the shot peening application in fatigue life improvement. Using a CT-specimen, the study of shot peening effect on fatigue life was performed. Here, the compressive residual stress is converted into residual stress intensity factor, K res.. Together with the applied stress intensity factor, K apl. , the superposition principle can be used. The result of the investigation clarifies quantitatively what has been widely believed that one of the easiest ways to improve fatigue life is by perfecting the surface via shot peening. Compressive stresses are beneficial not only in postponing fatigue crack initiation but also in preventing the crack propagation, which lead to increasing fatigue strength.

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$Research paper thumbnail of Incorporating the morphological difference of corrosion cracks in computational fracture mechanics approach$

Incorporating the morphological difference of corrosion cracks in computational fracture mechanics approach

Computational Materials Science, Apr 1, 2012

This paper encourages materials scientists to incorporate computational approach in their researc... more This paper encourages materials scientists to incorporate computational approach in their research. At the same time it gives a warning on how to use it, especially for stress corrosion cracking (SCC), since any continuum approach is highly dependent upon the shape of the crack. Evaluating the basic morphology of the SCC behavior of steels shows that each microstructure produces unique shape that can be used as a foundation for computational model creation.

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