Failures of Shafts

2021 ◽  
pp. 349-378
Author(s):  
Brett A. Miller ◽  
Phillip Swartzentruber
Keyword(s):  
Brittle Fracture ◽  
Ductile Fracture ◽  
Contact Fatigue ◽  
Rotary Motion ◽  
Background Information ◽  
Linear Motion ◽  
Fatigue Wear ◽  
Bending Fatigue ◽  
Torsional Fatigue ◽  
Stress Raisers

Abstract In addition to failures in shafts, this article discusses failures in connecting rods, which translate rotary motion to linear motion (and conversely), and in piston rods, which translate the action of fluid power to linear motion. It begins by discussing the origins of fracture. Next, the article describes the background information about the shaft used for examination. Then, it focuses on various failures in shafts, namely bending fatigue, torsional fatigue, axial fatigue, contact fatigue, wear, brittle fracture, and ductile fracture. Further, the article discusses the effects of distortion and corrosion on shafts. Finally, it discusses the types of stress raisers and the influence of changes in shaft diameter.

scholarly journals A New Fracture Analysis Technique for Charpy Impact Test Using Image Processing

2021 ◽  
Vol 59 (1) ◽  
pp. 61-66
Author(s):  
Tae Chang Park ◽  
Beom Suk Kim ◽  
Ji Hee Son ◽  
Yeong Koo Yeo
Keyword(s):  
Image Processing ◽  
Brittle Fracture ◽  
Ductile Fracture ◽  
Impact Test ◽  
Charpy Impact ◽  
Charpy Impact Test ◽  
Fracture Analysis ◽  
Binary Image ◽  
Fracture Area ◽  
Brittle Fractures

The Charpy impact test is used to identify the transition between ductility and brittleness. The percentages of ductile and brittle fractures in steel can be evaluated based on each fracture area, which is presently determined by an analyzer with the naked eye. This method may lead to subjective judgement, and difficulty accurately quantifying the percentage. To resolve this problem, a new analysis method based on image processing is proposed in this study. A program that can automatically calculate the percentage of the ductile and brittle fractures has been developed. The analysis is performed after converting an RGB fracture image into a binary image using image processing techniques. The final binary image consists of 0 and 1 pixels. The parts with the pixel values of 1 correspond to the brittle fracture areas, and the pixel values of 0 represent the ductile fracture areas. As a result, by counting the number of 0 pixels in the entire area, it is possible to automatically calculate the percentage of ductile fracture. Using the proposed automatic fracture analysis program, it is possible to selectively distinguish only the brittle fracture from the entire fracture area, and to accurately and quantitatively calculate the percentages of ductile and brittle fractures.

scholarly journals Effect of Gas Nitriding on Interface Adhesion and Surface Damage of CL60 Railway Wheels under Rolling Contact Conditions

Metals ◽  
2020 ◽  
Vol 10 (7) ◽  
pp. 911
Author(s):  
Qiang Wu ◽  
Tao Qin ◽  
Mingxue Shen ◽  
Kangjie Rong ◽  
Guangyao Xiong ◽  
...  
Keyword(s):  
Wear Behavior ◽  
Rolling Contact Fatigue ◽  
Contact Fatigue ◽  
Rolling Contact ◽  
Wheel Surface ◽  
Fatigue Wear ◽  
Material Loss ◽  
Surface Protection ◽  
Gas Nitriding ◽  
Railway Wheels

The influence of surface gas nitriding on wheel/rail rolling contact fatigue and wear behavior of CL60 wheel was studied on a new rolling contact fatigue/wear tester (JD-DRCF/M). The failure mechanisms of the wheel/rail surface after the gas nitriding and without gas nitriding on the wheel surface were compared and analyzed. The results show that the wheel with gas nitriding could form a dense and hard white bright layer which was approximately 25 μm thick and a diffusion layer which was approximately 70 μm thick on the wheel surface. Thus, the gas nitriding on the railway wheel not only significantly improved the wear resistance on the surface of the wheel, but also effectively reduced the wear of the rail; the results show that the material loss reduced by 58.05% and 10.77%, respectively. After the wheel surface was subjected to gas nitriding, the adhesive coefficient between the wheel/rail was reduced by 11.7% in dry conditions, and was reduced by 18.4% in water media, but even so, the wheel with gas nitriding still could keep a satisfactory adhesive coefficient between the wheel/rail systems, which can prevent the occurrence of phenomena such as wheel-slip. In short, the gas nitriding on the wheel surface can effectively reduce the wear, and improve the rolling contact fatigue resistance of the wheel/rail system. This study enlarges the application field of gas nitriding and provides a new method for the surface protection of railway wheels in heavy-duty transportation.

scholarly journals Comparative Study on the Friction Property of Bearing Steel Modified Bygraphite/MoS2 Composite Coating and Manganese Phosphate Coating

2019 ◽  
Vol 25 (4) ◽  
pp. 383-393 ◽  
Author(s):  
Libin ZANG ◽  
Yong CHEN ◽  
Lixin RAN ◽  
Yang ZHENG ◽  
Kai LI ◽  
...  
Keyword(s):  
Surface Modification ◽  
Tribological Properties ◽  
High Performance ◽  
Contact Fatigue ◽  
Bearing Steel ◽  
Phosphate Coating ◽  
Wear Properties ◽  
Fatigue Wear ◽  
Manganese Phosphate ◽  
Lubrication Performance

Surface modification is an important method to improve the contact fatigue life of transmission parts. The preparation of high performance coating with good tribological properties on the gears and bearings has become the research trends. This paper presents graphite/MoS2 composite spray and manganese phosphate conversion coating prepared on the AISI52100 steel surface and investigates their anti-fatigue mechanism. The tribological properties of the modified layers were studied using a SRV-IV multifunctional friction and wear tester. The microstructure and interfacial components of the coating and wear surfaces were analyzed by SEM and EDS, respectively. The surface morphology and phase composition of the coating were evaluated through laser 3D microscopy and XRD analyses, respectively. Both modified layers showed good anti-friction and anti-wear properties. The friction coefficients of the surfaces modified by manganese phosphate coating and graphite/MoS2 decreased by 7 % and 14 %, respectively, and the corresponding extreme pressure properties increased by 11 % and 55 %, respectively. But the mechanism of anti-fatigue wear and the corresponding interfacial phenomena of the surface modification of the graphite/MoS2 composite spraying layer is different from those of manganese phosphate coating. The hard-ceramic particles with graphite and MoS2 are sprayed on the substrate to obtain the surface hardening layer, resulting in higher wear resistance. The graphite and MoS2 modified layer can greatly reduce the friction coefficient and improve the lubrication performance on the surface. Manganese phosphate coating serves as a chemical soft coating and is filled with rough corrugated caused by surface processing, which induces an ideal meshing surface after initial friction phase. The obtained hole-shaped structure and "infiltration" role contribute to the storage of lubricants and thus improves the lubrication performance.

Fatigue Behaviour of DLC Coated Al 7075-T6 Alloy in an Aggressive Mixture

2014 ◽  
Vol 627 ◽  
pp. 81-84 ◽  
Author(s):  
Sergio Baragetti ◽  
Riccardo Gerosa ◽  
Francesco Villa
Keyword(s):  
High Performance ◽  
Contact Fatigue ◽  
Fatigue Behaviour ◽  
Fatigue Tests ◽  
Structural Elements ◽  
Pvd Coatings ◽  
Bending Fatigue ◽  
Al 7075 ◽  
Rotating Bending Fatigue ◽  
Rotating Bending

7075-T6 aluminium alloy is commonly adopted in high performance structures and components. Its fatigue behaviour is however dramatically worsened by exposure to aggressive environments. The deposition of PVD coatings, which are commonly adopted to increase the surface properties of structural elements in terms of hardness, contact fatigue and wear resistance, could be beneficial also for the fatigue behaviour of a 7075-T6 substrate in an aggressive environment. In the present work, Diamond Like Carbon (DLC) PVD coated 7075-T6 specimens immersed in methanol have been analysed, by means of step-loading rotating bending fatigue tests (R = -1) at 2·105 cycles. Coated specimens were tested in laboratory air for comparison, and uncoated polished samples were studied in both the environments to obtain reference values. SEM micrographs of the fracture surfaces were taken to investigate the effects of the corrosive environment on the failure mechanism.

scholarly journals Study on Friction and Lubrication Characteristics of Surface with Unidirectional Convergence Texture

Coatings ◽  
2019 ◽  
Vol 9 (12) ◽  
pp. 780 ◽  
Author(s):  
Chenchen Li ◽  
Xuefeng Yang ◽  
Shouren Wang ◽  
Yanjun Wang ◽  
Chongyang Lu ◽  
...  
Keyword(s):  
Friction Coefficient ◽  
Abrasive Wear ◽  
Simulation Analysis ◽  
Dynamic Pressure ◽  
Contact Fatigue ◽  
Hydrodynamic Pressure ◽  
Surface Friction ◽  
Textured Surface ◽  
Fatigue Wear ◽  
Lubrication Performance

In order to study the influence of texture on the wear and lubrication performance of the surface of the tools, three kinds of textures with unidirectional convergence morphology were processed on the surface of the samples, and each texture was designed with different area occupancy ratios. Simulation analysis shows that, owing to the reflow and convection effect of liquid in the texture, the lubricating film flowing through the textured surface has a high hydrodynamic pressure value, and the semicircular ring texture is the most prominent. By comparing the friction coefficient, when the area occupancy ratio of texture on the surface is 10%, the surface of the samples with different morphology has the lowest coefficient of friction; the friction coefficient of the semicircular ring textured surface is especially very low. Surface textures reduce the direct contact area between the friction pairs, and generate dynamic pressure lubrication and secondary lubrication, so that the surface friction coefficient of the samples is obviously reduced. The surfaces of the non-textured samples have abrasive wear and contact fatigue wear, and the surfaces of the textured samples have adhesive wear, abrasive wear, and cavitation.

scholarly journals IMCs Microstructure Evolution Dependence of Mechanical Properties for Ni/Sn/Ni Micro Solder-Joints

Materials ◽  
2020 ◽  
Vol 13 (1) ◽  
pp. 252 ◽  
Author(s):  
Ning Ren ◽  
Heng Fang ◽  
Dong Wang ◽  
Chenyi Hou ◽  
Yatao Zhao ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Brittle Fracture ◽  
Ductile Fracture ◽  
Solder Joints ◽  
Volume Fraction ◽  
Tensile Tests ◽  
Stress Concentrations ◽  
Element Analysis ◽  
Scale Down ◽  
Long Rod

The current miniaturization trend of microelectronic devices drives the size of solder joints to continually scale down. The miniaturized joints considerably increase intermetallic compounds (IMCs) volume fraction to trigger mechanical reliability issues. This study investigated precise relationships between varying IMC volumes and mechanical properties of Ni/Sn(20μm)/Ni micro-joints. A designed method that followed the IMC volume as the only variable was used to prepare micro-joint samples with different IMC volumes. The continuously thickened Ni3Sn4 IMCs exhibited a noticeable morphology evolution from rod-like to chunky shape. The subsequent tensile tests showed unexpected tensile strength responses as increasing Ni3Sn4 volume, which was strongly associated with the Ni3Sn4 morphological evolutions. Fractographic analysis displayed that the ductile fracture dominates the 20%–40% IMC micro-joints, whereas the brittle fracture governs the 40%–80% IMC micro-joints. For the ductile fracture-dominated joints, an abnormal reduction in strength occurred as increasing IMCs volume from 20% to 40%. This is primarily due to severe stress concentrations caused by the transformed long rod-typed morphology of the Ni3Sn4. For the brittle fracture-dominated joints, the strength appeared a monotonous increase as the Ni3Sn4 volume increased. This may be attributed to the increased crack resistance resulting from continuous coarsening of the chunky Ni3Sn4 without any voids. Moreover, the finite element analysis was provided to further understand the joint failure mechanisms.

Effects of Rolling on Load Bearing Capacity of Sintered Metal Gears

2007 ◽  
Author(s):  
Takao Koide ◽  
Takatoshi Maemori ◽  
Teruie Takemasu ◽  
Kouitsu Miyachika ◽  
Chiaki Namba
Keyword(s):  
Bearing Capacity ◽  
Surface Properties ◽  
Contact Fatigue ◽  
Fatigue Tests ◽  
Load Bearing Capacity ◽  
Load Bearing ◽  
Bending Fatigue ◽  
Gear Teeth ◽  
Sintered Metal

This paper describes the effects of surface rolling on the load bearing capacity of sintered metal gears. Sintered metal gears and rollers were surface-rolled under various amounts of rolling. The effects of rolling on the surface properties were examined by measuring the porosities and hardness near the surfaces of the rolled gear teeth and rollers. Bending fatigue tests for the surface-rolled sintered metal gears and contact fatigue tests for the rollers were carried out. The effects of the amount of rolling on the load bearing capacity of sintered metal gears and rollers were determined, and these results were compared with the results for as-sintered and wrought steel gears and rollers.

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