A Mechanics Analysis of Formation and Expansion of Fatigue Crack in Laser Cladding on Repeated Impact Load

2008 ◽  
Vol 392-394 ◽  
pp. 109-115
Author(s):  
Ge Yan Fu ◽  
Shi Hong Shi
Keyword(s):  
Laser Cladding ◽  
Impact Load ◽  
Vacancy Concentration ◽  
Coating Material ◽  
Dispersion Strengthening ◽  
Impact Fatigue ◽  
Repeated Impact ◽  
Fine Crystal ◽  
Impact Compression ◽  
Combined Action

Coating samples prepared by laser cladding were subjected to repeated impact fatigue experiment. It is observed through phenomenological analysis that most coating cracks are original from the surface. And then, the cracks extend by the combined action of coating inner stress and repeated impact compression stress. The formation of crack is close related to performance of coating material. It can be divided to traversed crack and reticular crack from surface side; it also can be divided to vertical extend crack and reticular extend crack from the cross section side. Rigid and brickle coating has a shorter repeated impact life because a kind of linear crack is formed easily in it. On the other hand, tougher coating has a long life. Mechanics of nucleation and expansion of crack was explained by using stress concentration theory and vacancy concentration theory. The anti-repeated impact fatigue performance of laser cladding part could be improved by increasing toughness and reducing hardness of the coating material. Furthermore, suitable dispersion strengthening and fine-crystal strengthening can obtain the same purpose.

Mechanics Behavior Analysis on Laser Cladding under Repeated Impacting Load

2010 ◽  
Vol 154-155 ◽  
pp. 1100-1103
Author(s):  
Ru Shu Peng ◽  
De Wen Tang ◽  
Qiong Liu
Keyword(s):  
Behavior Analysis ◽  
Stress Wave ◽  
Laser Cladding ◽  
Impact Load ◽  
Joint Surface ◽  
Impact Loads ◽  
Repeated Impact ◽  
Hardness Change

On the property of repeated impact load, the attrition, hardening and plasticity warp of the laser cladding sampling were researched by using stress wave spread theory. Results show that under repeated impact loads, stress wave occurs on the metallurgical joint surface of the coat and the basis, forming stretch wave that causes coat slitting and angle splitting. The micro-pits failure and deep exfoliation occur on the coat surface because of the stress centralization. The accumulation of impact load energy cause hardness change and plasticity warp.

Hot Affect Region of Base Clad by Laser Beam and its Repeated-Impact Properties

2007 ◽  
Vol 10-12 ◽  
pp. 610-614
Author(s):  
Shi Hong Shi ◽  
Ming Di Wang
Keyword(s):  
Stainless Steel ◽  
Laser Beam ◽  
Laser Cladding ◽  
Impact Load ◽  
Repeated Impact ◽  
Impact Properties ◽  
Austenite Stainless Steel ◽  
Low Stiffness

The experiment result of base of laser cladding samples shows that more energy base absorb, more wide the Hot affect region. The base with the quenchable material will be quenched hardening and get refinement organization, such as medium steel, etc. Contrariwise the base of austenite stainless steel doesn’t have these phenomenons. Under the repeated impact load, the quenched hardening base may be softened and appear flaw easily, such as crack, etc. The base of low stiffness may be hardened in a distance.

scholarly journals Impact Response of Hammerhead Pier Fibrous Concrete Beams Designed with Topology Optimization

2020 ◽  
Author(s):  
Meivazhisalai Parasuraman Salaimanimagudam ◽  
Covaty Ravi Suribabu ◽  
Gunasekaran Murali ◽  
Sallal R. Abid
Keyword(s):  
Topology Optimization ◽  
Concrete Beams ◽  
Impact Load ◽  
Impact Resistance ◽  
Adaptive Mesh ◽  
Impact Response ◽  
Adaptive Meshing ◽  
Repeated Impact ◽  
Ductility Ratio ◽  
The Impact

Reducing the weight of concrete beams is a primary (beyond strength and durability) concern of engineers. Therefore, this research was directed to investigate the impact response of hammerhead pier concrete beams designed with density-based method topology optimization. The finite element topology optimization was conducted using Autodesk fusion 360 considering three different mesh sizes of 7 mm, 10 mm, and adaptive meshing. Three optimized hammerhead beam configurations; HB1, HB2, and HB3, respectively, with volume reductions greater than 50 %. In the experimental part of this research, nine beams were cast with identical size and configuration to the optimized beams. Three beams, identical to the optimized beams, were tested under static bending for verification purposes. In comparison, six more beams, as in the preceding three beams but without and with hooked end steel fibers, were tested under repeated impact load. The test results revealed that the highest flexural capacity and impact resistance at crack initiation and failure were recorded for the adaptive mesh beams (HB3 and HB3SF). The failure impact energy and ductility ratio of the beam HB3SF was higher than the beams HB1SF and HB2SF by more than 270 %. The results showed that the inclusion of steel fiber duplicated the optimized beam’s impact strength and ductility several times. The failure impact resistance of fibrous beams was higher than their corresponding plain beams by approximately 2300 to4460 %, while their impact ductility ratios were higher by 6.0 to 18.1 times.

Effect of Al2O3 Xerogel on the Microstructure and the Properties of Laser Cladding Coating of Fe-Based Alloy

2010 ◽  
Vol 434-435 ◽  
pp. 743-746
Author(s):  
Shi Hai Zhao ◽  
Xiu Ming Jiang ◽  
Xu Guo Huai ◽  
Xiao Wei Fan
Keyword(s):  
Wear Resistance ◽  
Laser Cladding ◽  
Continuous Wave ◽  
Continuous Wave Laser ◽  
Dispersion Strengthening ◽  
X Ray Diffraction ◽  
X Ray ◽  
Al2o3 Particles ◽  
Molten Liquid ◽  
Steel Substrates

Laser cladding Fe-based alloy coatings with 0, 3, 6, 9, 12 and 15% Al2O3 xerogel on 45 steel substrates were prepared by 5kWCO2 continuous wave laser. The effect of the content of Al2O3 xerogel on the microstructure, microhardness and wear resistance of the coatings was investigated by scan electron microscope, X-ray diffraction. The results show that the microstructure and properties were different when the content of Al2O3 xerogel changed. The addition of Al2O3 xerogel can enhance the fluidity of molten liquid and refine the microstructure. Adding adequate amount of Al2O3 xerogel to Fe-based alloy can improve the hardness and the wear resistance due to the nano-Al2O3 particles on surfaces and the dispersion strengthening and hardening of nano- Al2O3 particles.

scholarly journals Comparison of Lifetime of the PVD Coatings in Laboratory Dynamic Impact Test and Industrial Fine Blanking Process

Materials ◽  
2020 ◽  
Vol 13 (9) ◽  
pp. 2154
Author(s):  
Josef Daniel ◽  
Radek Žemlička ◽  
Jan Grossman ◽  
Andreas Lümkemann ◽  
Peter Tapp ◽  
...  
Keyword(s):  
Impact Test ◽  
Impact Load ◽  
Protective Coatings ◽  
Impact Testing ◽  
Pvd Coatings ◽  
Dynamic Impact ◽  
Repeated Impact ◽  
Suitable Alternative ◽  
Fine Blanking ◽  
Blanking Process

Protective hard PVD coatings are used to improve the endurance of the tools exposed to repeated impact load, e.g., fine blanking punches. During the fine blanking process, a coated punch repeatedly impacts sheet metal. Thus, the coating which protects the punch surface is exposed to the dynamic impact load. On the other hand, the laboratory method of dynamic impact testing is well known and used for the development and optimization of protective coatings. This paper is focused on the comparison of tool life and lifetime of the industrial prepared PVD coatings exposed to repeated dynamic impact load in the industrial fine blanking process and the laboratory dynamic impact testing. Three different types of protective coatings were tested and the results were discussed. It was shown that the lifetime of coated specimens in both the fine blanking and the dynamic impact processes was influenced by similar mechanical properties of the protective coatings. The qualitative comparison shows that the lifetime obtained by the dynamic impact test was the same as the lifetime obtained by the industrial fine blanking process. The laboratory impact test appears to be a suitable alternative for the optimisation and development of protective PVD coatings for punches used in the industrial fine blanking process.

Crack Propagation of CCT Foam Specimen under Impact Fatigue

2010 ◽  
Vol 118-120 ◽  
pp. 32-36 ◽  
Author(s):  
Jae Ung Cho ◽  
Li Yang Xie ◽  
Chong Du Cho ◽  
Sang Kyo Lee
Keyword(s):  
High Strain Rate ◽  
Impact Loading ◽  
High Strain ◽  
Nickel Foam ◽  
Fatigue Properties ◽  
Foam Material ◽  
Impact Fatigue ◽  
Repeated Impact ◽  
Repeated Impacts ◽  
The Impact

The objective of this study is to investigate the effect of the low or high strain rate on the impact fatigue properties of the nickel foam material and to understand the lifetime of this material which is subjected to the repeated impacts at different energy levels. Failures of foam materials under single and repeated impacts analogous to fatigue are essential to designers and users in military and aerospace structures. The material failure induced by repeated impact loading becomes a critical issue because of significant loss of stiffness and compressive strength in the foam material. Testing methods to study impact(that is, high strain rate) fatigue are quite numerous; no single standard testing procedure is defined for studying the impact fatigue property of a material. The increasing application of foam material in aerospace structures, owing to high specific stiffness and strength has attracted a great concern about the high sensitivity to impact damage introduced during manufacture or in service, and the effects of such damage on structural degradation. To investigate this issue, this study sets up an experimental procedure to determine the impact fatigue properties of nickel foam material. This study performs both experimental and numerical investigations to catch the impact fatigue behavior of nickel foam with open type. Design life and probability of failure or survival at specified life can be calculated so that the fatigue life of nickel core material subjected to repeated impact loading is predicted.

Sign in / Sign up

Export Citation Format

Share Document