No abstract

The initial induced compressive residual stresses relax during component operating life and it is important to consider the relaxation phenomenon in the design of the component. In this study, 2024-T 351 aluminium alloy specimens were shot peened under three different shotpeening intensities. Cyclic tests for two load magnitudes were performed for 1, 2, 10, 1000 and 10,000 cycles. The initial and final residual stresses and the cold work after each loading cycle were measured for the three shot-peening intensities and for the two load magnitudes using X-ray diffraction. The initial and final microhardnesses after each loading cycle load were also measured for the three shot-peening intensities. The results showed that the reduction in the residual stress, microhardness and cold work are dependent on the applied load. An empirical model was proposed to estimate the residual stress relaxation. The presented model incorporates parameters including the degree of cold work, initial induced residual stress and the number of applied loading cycles.

No abstract

No abstract

Shot peening process is a cold performed function to enhance the mechanical properties which is widely used in many industries. This process introduces compressive residual stress which was proven to increase the fatigue life, geometry stability and corrosion resistance. However, the benefit of the residual stress is still unstable due to the relaxation during the operation. This paper will study on the trend of the relaxation of residual stress against cyclic loading as well as the change in the hardness. The material used in this study is carbon steel ASTM A516/ SA 516 Grade 70. Shot peening process with steel shots was applied to the samples to introduce compressive residual stress in the samples. Cyclic load was applied to samples after shot peening process with low load of 52Mpa (20% of Yield Strength) and high load of 208Mpa (80% of Yield Strength). The measurement of residual stress using X-Ray diffraction and hardness test was done on the samples to study the trend of the relaxation of residual stress and the change in hardness values. The result shows that more relaxation of residual stress occurs if the applied cyclic load is higher. The change of hardness trend is found non-sequenced in this study due to random coverage of shot peening.

Abstract. This paper investigate the performance of banana fibre reinforced slabs 300mm x 300mm size with varied thickness subjected to low impact projectile test. A self-fabricated drop-weight impact test rig with a steel ball weight of 1.25 kg drop at 1 m height has been used in this research work. The main variables for the study is to find the relationship of the impact resistance against the BF contents and slab thickness. A linear relationship has been established between first and ultimate crack resistance against BF contents and slab thickness by the experiment. The linear relationship has also been established between the service (first) crack and ultimate crack resistance against the BF contents for a constant spacing for various banana fibre reinforced slab thickness. The increment in BF content has more effect on the first crack resistance than the ultimate crack resistance. The linear relationship has also been established between the service (first) crack and ultimate crack resistance against the various slab thickness. Overall 1.5% BF content with slab thickness of 40 mm exhibit better first and ultimate crack resistance up to 16 times and up to 17 times respectively against control slab (without BF)

No abstract

Problem statement: Compressive residual stress induced by surface treatment such as shot peening increased component’s fatigue life. However the initial induced residual stresses relax during component operating life and it is important to consider the relaxation in the design. Approach: In this study, a 2024-T351 aluminum alloy specimens were shot peened into three shot peening intensities condition to induce compressive residual stresses. Then fatigue test for two loads was performed for the 10, 1000 and 10000 cyclic loads. The initial residual stresses at the initial condition and after 10, 1000 and 10000 cycle of fatigue loading were measured using X-ray diffraction method. Results: The results showed that the relaxation of the residual stress for the load 15.5 kN is less than the relaxation of the load 30 kN for the three shot peening intensity. The maximum relaxation for load 15.5 kN is 46% of the initial residual stress at 10000 cycles for intensity 0.009 A while the maximum relaxation for load 30 kN is 54% at 10000 cycles for the intensity of 0.0054% A. this result indicated that the residual stress relaxation depended on the load amplitude. Conclusion: The initial residual stress did not remain stable during the component’s fatigue life. Within the second phase relaxation, micro-plastic strains accumulating from cycle to cycle. The residual stress relaxation for second phase is in logarithmic relationship