EFFECT OF TEMPERATURE ON THE FRACTURE MODES OF BHW-35 STEEL UNDER MODE-Ⅱ LOADING

Finite element method(FEM)has been used to analyze the stress and strain fields and the stress tri-axial levels around the tip of the crack under mode-Ⅱ loading.The results show that: under mode-Ⅱ loading,the direction of the maximum tensile stress and that of the maximum tri-axial levels(R_ )exist at an angle of-75.3°from the original crack plane:the maximum shear stress and R_ =0 exist along the original crack plane. Mode-Ⅱ loading experiment using BHW-35 steel at different temperatures show that there are two kinds of fracture mode.opening mode(or tensile mode)and sliding mode(or shear mode).A de- crease in temperature causes the fracture mode to change from shear mode to tensile mode.For BHW- 35 steel,this critical temperature is about-90C.Actually.under any kind of loading mode(mode Ⅰ,mode Ⅱ,mode Ⅲ or mixed mode),there always exist several kinds of potenital fracture modes (for example,opening mode.sliding mode.tearing mode or mixed mode).The effect of temperature under mode-Ⅱ loading is actually related to the change of the elastic-plastic properties of the material.

Effect of specimen thickness on Mode Ⅱ fracture toughness of rock

Anti symmetric four point bending specimens with different thickness, without and with guiding grooves, were used to conduct Mode Ⅱ fracture test and study the effect of specimen thickness on Mode Ⅱ fracture toughness of rock. Numerical calculations show that the occurrence of Mode Ⅱ fracture in the specimens without guiding grooves (when the inner and outer loading points are moved close to the notch plane) and with guiding grooves is attributed to a favorable stress condition created for Mode Ⅱ fracture, i.e. tensile stress at the notch tip is depressed to be lower than the tensile strength or to be compressive stress, and the ratio of shear stress to tensile stress at notch tip is very high. The measured value of Mode Ⅱ fracture toughness K ⅡC decreases with the increase of the specimen thickness or the net thickness of specimen. This is because a thick specimen promotes a plane strain state and thus results in a relatively small fracture toughness.

MECHANISM ANALYSIS OF THICKNESS EFFECT ON MIXED MODE Ⅰ/Ⅱ FRACTURE OF LC4-CS ALUMINUM ALLOY

Mixed mode Ⅰ/Ⅱ fracture erperiments of LC4-CS aluminum alloy were conductedby using tension--shear specimens with thicknesses of 2, 4, 8 and 14mm. Fracturemechanisms of thickness effect on mixed mode Ⅰ/Ⅱ fracture were first examined fromfracture surface morphology to correlate with the macroscopic fracture behavior andstress state. It is found that specimen thickness has a strong influence on mixed modefracture. As thickness varies from thin to thick the macroscopic fracture surfacesappear the characteristics of plane stress state (2mm, 4mm--thick specimen), three--dimensional stress state (8mm--thick specimens), and plane strain state (14mm--thickspecimens), respectively. The specimens of all kinds of thicknesses are typical of ten-sile type failure under mode Ⅰ loading condition and shear type failure under mode Ⅱloading condition. Two distinct features coexist on the fracture surfaces under mixedmode loading conditions, and the corresponding proportion varies with loading mix-ity. Void--growth processes are the failure mechanism in both predominately tensile-and shears--type fractures. The size and depth of dimples on the fracture surface varygreatly with thickness. Therefore, it is extraordinary necessary to take into accountthe thickness effect when a mixed mode fracture criterion is being established.

Dynamic ModeⅡfracture behavior of rocks under hydrostatic pressure using the short core in compression(SCC)method

The shear failure of rocks under both a static triaxial stress and a dynamic disturbance is common in deep underground engineering and it is therefore essential for the design of underground engineering to quantitively estimate the dynamic ModeⅡfracture toughness KⅡCof rocks under a triaxial stress state.However,the method for determining the dynamic KⅡCof rocks under a triaxial stress has not been developed yet.With an optimal sample preparation,the short core in compression(SCC)method was designed and verified in this study to measure the dynamic KⅡCof Fangshan marble(FM)subjected to different hydrostatic pressures through a triaxial dynamic testing system.The formula for calculating the dynamic KⅡCof the rock SCC specimen under hydrostatic pressures was obtained by using the finite element method in combination with secondary cracks.The experimental results indicate that the failure mode of the rock SCC specimen under a hydrostatic pressure is the shear fracture and the KⅡCof FM increases as the loading rate.In addition,at a given loading rate the dynamic rock KⅡCis barely affected by hydrostatic pressures.Another important observation is that the dynamic fracture energy of FM enhances with loading rates and hydrostatic pressures.

Experimental study on time-dependent stress and strain of in-plane shear(ModeⅡ) fracture process of rock

Shear-box test with strain measurement was used to study time-dependent stress and strain of in-plane shear(Mode Ⅱ) fracture process of rock and to reveal the mechanism of Mode Ⅱ fracture.Numerical results show that the maximum shear stress τmax at the crack tip is much larger than the maximum tensile stress σ1 and the ratio of τmax/σ1 is about 5,which favors Mode Ⅱ fracture of rock.Test results indicate that the strain-time curve comprises three stages:the linear deformation stage,the micro-cracking stage and the macroscopic crack propagation.The strain in the direction of the original notch plane is negative,due to restraining effect of compressive loading applied to the original notch plane.Both σ1 and τmax are increased as the load increases,but the slope of τmax is larger than that of σ1 and the value of τmax is always larger than that of σ1.Therefore,τmax reaches its limited value at peak load before σ1 and results in Mode Ⅱ fracture of rock.Shear-box(i.e.compression-shear) test becomes a potential standard method for achieving the true Mode Ⅱ fracture and determining Mode Ⅱ fracture toughness of rock.

Teriparatide anabolic therapy as potential treatment of type Ⅱ dens non-union fractures

Odontoid fractures account for 5% to 15% of all cervical spine injuries and 1% to 2% of all spine fractures. Type Ⅱ fractures are the most common fracture pattern in elderly patients. Treatment(rigid and non-rigid immobilization, anterior screw fixation of the odontoid and posterior C1-C2 fusion) remains controversial and represents a unique challenge for the treating surgeon. The aims of treatment in the elderly is to quickly restore pre-injury function while decreasing morbidity and mortality associated with inactivity, immobilization with rigid collar and prolonged hospitalization. Conservative treatment of type Ⅱ odontoid fractures is associated with relatively high rates of non-union and in a few cases delayed instability. Options for treatment of symptomatic non-unions include surgical fixation or prolonged rigid immobilization. In this report we present the case of a 73-year-old woman with post-traumatic odontoid nonunion successfully treated with Teriparatide systemic anabolic therapy. Complete fusion and resolution of the symptoms was achieved 12 wk after the onset of the treatment. Several animal and clinical studies have confirmed the potential role of Teriparatide in enhancing fracture healing. Our case suggests that Teriparatide may have a role in improving fusion rates of C2 fractures in elderly patients.

PFNA-Ⅱ combined with preoperative accurate measurement evaluation for the treatment of senile femoral fractures between rotor

Objective:Research PFNA-Ⅱcombined with preoperative accurate measurement of senile femoral fracture between the rotor of the clinical application value.Methods:Fiftytwo patients with intertrochanteric fractures admitted to our hospital from January 2017 to October 2019 were selected and divided into the traditional group and the measurement group according to the random number table method,with 26 patients in each group.The traditional group could not make accurate measurement before operation,but the measurement group could make accurate measurement before operation.Postoperative follow-up was conducted for at least 6 months to compare The Times of intraoperative X-ray fluoroscopy,operation time,intraoperative blood loss,and TAD,Harris score and improved BADL score of the hip joint between the two groups.Results:The number of intraoperative X-ray fluoroscopy in the measured group was less than that in the conventional group(15.08+/-2.10 vs 19.81±2.21 times,t=7.920,P=0.000).The operation time of the measured group was lower than that of the traditional group(78.46+/-3.68 vs 89.62+/-5.28 minutes,t=8.841,P=0.000).Intraoperative blood loss was less in the measured group than in the conventional group(146.15+/-24.18 vs 163.46+/-22.62 ml,t=2.666,P=0.010).There was no statistically significant difference in TAD values between the two groups(23.73+/-2.49 vs 24.04+/-2.63 mm,t=0.433,P=0.667).There is no interaction between intervention mode and time factor(F=0.362,P=0.698).There was statistical difference in Harris scores between different timepoints before and after the operation,in other words,there was time effect(F=378.110,P=0.000).There was no statistical difference in Harris scores between the 2 groups,in other words,there was no group effect(F=0.874,P=0.354).All the Harris scores of the two groups increased with time,and the increase trend was consistent(39.69+/-3.27,68.27+/-5.06,82.54+/-6.21 points,F=49.333,P=0.000;39.15+/-3.46,67.00+/-4.24,80.84+/-7.12 points,F=53.460,P=0.000).There was no significant difference in the improved BADL score between the two groups 6 months after surgery(t=0.587,P=0.560).Conclusion:PFNA-Ⅱcombined with preoperative accurate measurement in the application of the elderly femoral fracture between the rotor is safe and effective,not only can shorten the operation time,less intraoperative blood loss and the number of perspective,while reducing the risks of medical radiation.

三步接骨法治疗Sanders Ⅱ型跟骨骨折的有限元研究

目的量化评估三步接骨法治疗Sanders Ⅱ型跟骨骨折效能指标,阐明其科学机制。方法利用健康成年男性踝关节CT数据,构建正常足踝模型与Sanders Ⅱ型跟骨骨折模型,在骨折模型上进行三步接骨法的力学加载,模拟拔伸牵引、提按顶复、端挤捏骨等手法,评估跟骨复位情况并求解不同手法作用下力学的变化。结果建立正常足部模型与Sanders Ⅱ A/B/C型跟骨骨折模型;三步接骨法加载复位后跟骨长、高、宽、Gissane’s角及Bohler’s角得到明显纠正;求解不同手法的力学趋势,发现拔伸牵引法能有效纠正重叠位移,提按顶复法侧重纠正前后侧移位,端挤捏骨法致力纠正内外侧移位。结论三步接骨法通过依次纠正骨折位移,能恢复跟骨解剖结构,有效治疗跟骨SandersⅡ型损伤,具有有效性及科学性。

续断接骨汤联合下肢洗伤方Ⅱ号熏蒸对膝关节骨折术后患者的影响

目的:分析续断接骨汤联合下肢洗伤方Ⅱ号熏蒸对膝关节骨折术后患者的影响。方法:选取2021年8月—2023年8月厦门大学附属第一医院思明院区收治的100例膝关节骨折术后患者。根据随机数表法将其分为对照组和观察组,各50例。两组均给予常规治疗,对照组给予下肢洗伤方Ⅱ号熏蒸治疗,观察组在对照组基础上给予续断接骨汤治疗。比较两组治疗前及治疗1周后膝部疼痛程度、膝部肿胀程度、炎症因子,治疗前及治疗8周后膝关节功能,生活质量。结果:治疗1周后,两组视觉模拟评分法(VAS)评分、膝部肿胀程度均降低,观察组VAS评分、膝部肿胀程度均低于对照组,治疗8周后,两组Lysholm评分升高,观察组Lysholm评分高于对照组,差异有统计学意义(P<0.05)。治疗1周后,两组白细胞介素-6(IL-6)、C反应蛋白(CRP)、肿瘤坏死因子-α(TNF-α)、降钙素原(PCT)水平均降低,观察组IL-6、CRP、TNF-α、PCT水平均低于对照组,差异有统计学意义(P<0.05)。治疗8周后,两组生理功能、生理职能、社会功能、躯体疼痛、精神健康、情感职能、活力、总体健康评分均升高,观察组生理功能、生理职能、社会功能、躯体疼痛、精神健康、情感职能、活力、总体健康评分均高于对照组,差异有统计学意义(P<0.05)。结论:续断接骨汤联合下肢洗伤方Ⅱ号熏蒸能够减轻膝关节骨折术后患者疼痛与膝部肿胀,有助于膝关节功能的快速恢复,能够控制机体的炎症反应,最终提高生活质量。

经跗骨窦切口与外侧L形切口钢板内固定治疗SandersⅡ、Ⅲ型跟骨骨折的疗效分析

目的分析SandersⅡ、Ⅲ型跟骨骨折患者采用经跗骨窦切口与跟骨外侧L形切口钢板内固定治疗的临床疗效。方法回顾性选取2017年9月至2021年3月池州市人民医院收治的62例SandersⅡ、Ⅲ型跟骨骨折患者,按照手术方式不同分为对照组和观察组,每组31例。其中,观察组采用经跗骨窦切口复位微型钢板内固定手术治疗,对照组采用跟骨外侧L形切口钢板内固定手术治疗。对比分析两组患者的手术相关指标、术后12个月跟骨Bohler角、Gissane角以及Marland足部功能评分,并比较术后并发症发生情况。结果62例患者均接受术后随访,随访时间13~16个月。术后6个月所有患者骨折均愈合,平均骨折愈合时间3~6个月。观察组患者的手术时间、手术切口分别为(53.1±10.3)min、(4.3±0.9)cm,明显短于对照组[(84.0±15.3)min、(11.1±1.2)cm],术后疼痛评分为(1.8±0.5)分,明显低于对照组[(3.2±1.1)分],差异均有统计学意义(P<0.05)。两组患者术后12个月Bohler角、Gissane角、Maryland足部功能评分比较,差异均无统计学意义(P>0.05)。观察组患者并发症发生率为6.45%,明显低于对照组(22.58%),差异有统计学意义(P<0.05)。结论经跗骨窦切口复位微型钢板内固定手术对SandersⅡ、Ⅲ型跟骨骨折患者造成的创伤较小,骨折复位及内固定强度效果明显,术后并发症发生率降低,足部功能恢复较快。

老年GardenⅠ~Ⅱ型股骨颈骨折病人采用半髋关节置换与内固定治疗的近期价值比较

目的探讨老年GardenⅠ~Ⅱ型股骨颈骨折病人采用半髋关节置换与内固定治疗的近期价值。方法2019年1月~2020年6月我院收治的老年股骨颈骨折病人102例,根据手术治疗方法将其分为对照组51例,观察组51例。对照组予以半髋关节置换术治疗,观察组予以内固定术治疗,比较两组手术相关指标、髋关节功能、髋周肌肉损伤、骨代谢指标及并发症发生情况。结果观察组手术时间、住院时间较对照组短,术中失血量明显较对照组少,观察组术后3及6个月Harris髋关节评分量表(HHS)评分低于对照组,两组比较差异有统计学意义(P<0.05);术后1年及2年,两组HHS评分比较无明显差异。观察组术后3天肌酸激酶(CK)、C反应蛋白(CRP)、白介素(IL)-6)均较同期对照组低,两组比较差异有统计学意义(P<0.05)。观察组术后3个月血清骨钙素蛋白(BGP)、骨碱性磷酸酶(ALP)及骨形态发生蛋白2(BMP-2)均明显较对照组低,两组比较差异有统计学意义(P<0.05);术后1年两组BGP、ALP、BMP-2比较无明显差异。观察组和对照组术后并发症发生率分别为9.80%和15.69%,两组比较差异无统计学意义(P>0.05)。结论老年GardenⅠ~Ⅱ型股骨颈骨折病人内固定术治疗近期效果与半髋关节置换术相当,且前者在手术时间、创伤等方面更具优势。

Experimental Study on Mixed-Mode(Ⅰ–Ⅱ)Fracture Toughness of Freshwater Ice

In recent years,the issue of aircraft icing has gained widespread recognition.The breaking and detachment of dynamic ice can pose a threat to flight safety.However,the shedding and fracture mechanisms of dynamic ice are unclear and cannot meet the engineering needs of ice-shedding hazard assessment.Therefore,studying the fracture toughness of ice bodies has extremely important practical significance.To address this issue,this article uses a centrally cracked Brazilian disk(CCBD)specimen to measure the pure modeⅠtoughness and pure modeⅡfracture toughness of freshwater ice at different loading rates.The mixed-mode(Ⅰ–Ⅱ)fracture characteristics of ice are discussed,and the experimental results are compared and analyzed with the theoretical values of the generalized maximum tangential stress(GMTS)criterion considering the influence of T-stress.The results indicated that as the loading rate increases,the pure modeⅠtoughness and pure modeⅡfracture toughness of freshwater ice decrease,and the fracture toughness of freshwater ice is more sensitive to the loading rate.Ⅰn terms of fracture criteria,the theoretical value of the ratio of pure modeⅡfracture toughness to pure modeⅠfracture toughness based on the GMTS criterion is in good agreement with the experimental value,while the theoretical value based on the maximum tangential stress(MTS)criterion deviates significantly from the experimental value,indicating that the GMTS criterion considering the influence of T-stress can better predict the experimental results.

A MIXED MODE FRACTURE CRITERION BASED ON THE MAXIMUM TANGENTIAL STRESS IN BRITTLE INCLUSION

A closed-form solution for predicting the tangential stress of an inclusion located in mixed mode Ⅰ and Ⅱ crack tip field was developed based on the Eshelby equivalent inclusion theory. Then a mixed mode fracture criterion, including the fracture direction and the critical load, was established based on the maximum tangential stress in the inclusion for brittle inclusioninduced fracture materials. The proposed fracture criterion is a function of the inclusion fracture stress, its size and volume fraction, as well as the elastic constants of the inclusion and the matrix material. The present criterion will reduce to the conventional one as the inclusion having the same elastic behavior as the matrix material. The proposed solutions are in good agreement with detailed finite element analysis and measurement.

Anisotropy in shear-sliding fracture behavior of layered shale under different normal stress conditions

Shear-sliding mode(mode Ⅱ)fracture of rocks is a vital failure form in deep underground engineering.To gain deep insight into the anisotropic shear fracture behaviors of a typical shale under high normal stress conditions,a series of direct shear tests were conducted on double-notched specimens in three typical bedding orientations(i.e.,the arrester,divider,short-transverse orientations)and under five normal stresses.The modeⅡfracture toughness(K_(Ⅱc))is found to exhibit a significant 3D anisotropy.The maximum K_(Ⅱc)is obtained in the divider orientation,followed by those in the arrester and short-transverse orientations.In contrast,the 3D anisotropy in the critical modeⅡenergy release rate(G_(Ⅱc))is not as significant as that in K_(Ⅱc),and G_(Ⅱc)in the arrester orientation is quite close to that in the divider orientation.The anisotropy in the prepeak input energy accumulated during shearing is found to be exactly consistent with that in G_(Ⅱc),which has not been noted before.Furthermore,the anisotropies in the modeⅡfracture resistances will,unexpectedly,not be weakened by the high normal stress.Owing to the layered structures,tensile cracks are involved during the modeⅡfracture process,resulting in the formation of rough fracture surfaces.

Shock-induced fracture of dolomite rock in small-scale blast tests

This paper attempts to study dolomite failure using small-scale blast tests.The experimental setup consisted of a cylindrical specimen with a central borehole fitted with a detonation cord inside a copper pipe.The specimen was confined using lead material.During the test,acceleration histories were recorded using sensors placed on the lead confinement.The results showed that heterogeneity and initial cracks significantly influenced the observed failure and cracking patterns.The tests were numerically represented using the previously validated Johnson-HolmquistⅡ(JH-2)constitutive model.The properties of the detonation cord were first determined and verified in a special test with a lead specimen to compare the deformation in the test with that of numerical simulation.Then,the small-scale blast test was simulated,and the failure of the dolomite was compared with the test observations.Comparisons of acceleration histories,scabbing failure,and number of radial cracks and crack density confirmed the overall repeatability of the actual testing data.It is likely that the proposed model can be further used for numerical studies of blasting of dolomite rock.

基于结构化变形驱动的非局部宏-微观损伤模型的真Ⅱ型裂纹模拟

Ⅱ型载荷作用下裂纹变形模式也为Ⅱ型的破坏问题称为真Ⅱ型破坏.准确定量地把握真Ⅱ型破坏的全过程是具有挑战性的问题.本文采用结构化变形驱动的非局部宏-微观损伤模型对真Ⅱ型破坏问题进行了模拟.根据结构化变形理论将点偶的非局部应变分解为弹性应变与结构化应变两部分,进而利用Cauchy-Born准则与结构化应变计算点偶的结构化正伸长量.在本文中,结构化应变取为非局部应变的偏量部分.当点偶的结构化正伸长量超过临界伸长量时,微细观损伤开始在点偶层次发展.将微细观损伤在作用域中进行加权求和得到拓扑损伤,并通过能量退化函数将其嵌入到连续介质-损伤力学框架中进行数值求解.进一步地,本文采用Gauss-Lobatto积分格式计算点偶的非局部应变,将积分点数目降低到4个,显著降低了前处理和非线性分析的计算成本.通过对Ⅱ型加载下裂尖应变场的分析揭示了采用偏应变作为结构化应变的原因.对两个典型真Ⅱ型破坏问题的模拟结果表明,本文方法不仅可以把握Ⅱ型加载下的真Ⅱ型裂纹扩展模式,同时可以定量刻画加载过程中的载荷-变形曲线,且不具有网格敏感性.最后指出了需要进一步研究的问题.

A MODE-Ⅱ GRIFFITH CRACK IN DECAGONAL QUASICRYSTALS

By using the method of stress functions, the problem of mode-Ⅱ Griffith crack in decagonal quasicrystals was solved. First, the crack problem of two-dimensional quasi-crystals was decomposed into a plane strain state problem superposed on anti-plane state problem and secondly, by introducing stress functions, the 18 basic elasticity equations on coupling phonon-phason field of decagonal quasicrystals were reduced to a single higher- order partial differential equations. The solution of this equation under mixed boundary conditions of mode-Ⅱ Griffith crack was obtained in terms of Fourier transform and dual integral equations methods. All components of stresses and displacements can be expressed by elemental functions and the stress intensity factor and the strain energy release rate were determined.

Microscopic characteristics of different fracture modes of brittle rock

Three types of rock specimens, three-point bending specimen, anti-symmetric four-point bending specimen and direct shearing specimen, were used to achieve Mode I, Mode II and mixed mode I–II fracture, respectively. Microscopic characteristics of the three fracture modes of brittle rock were studied by SEM technique in order to analyze fracture behaviors and better understand fracture mechanisms of different fracture modes of brittle rock. Test results show that the microscopic characteristics of different fracture modes correspond to different fracture mechanisms. The surface of Mode I fracture has a great number of sparse and steep slip-steps with few tearing ridges and shows strong brittleness. In the surface of Mode II fracture there exist many tearing ridges and densely distributed parallel slip-steps and it is attributed to the action of shear stress. The co-action of tensile and shear stresses results in brittle cleavage planes mixed with streamline patterns and tearing ridges in the surface of mixed mode I–II fracture. The measured Mode II fracture toughness K II C and mixed mode I–II fracture toughness K mC are larger than Mode I fracture toughness K I C · K II C is about 3.5 times K I C, and KmC is about 1.2 times K I C.

INTERTAN髓内钉与PFNA-Ⅱ治疗老年股骨粗隆间骨折的效果及对髋关节功能、生活质量的影响

目的:分析INTERTAN髓内钉与股骨近端防旋髓内钉-Ⅱ(PFNA-Ⅱ)治疗老年股骨粗隆间骨折的效果及对髋关节功能、生活质量的影响。方法:选取2017年10月—2020年9月北京燕化医院收治的80例老年股骨粗隆间骨折患者为研究对象。按照治疗方式的不同将其分两组,各40例。INTERTAN组实施INTERTAN髓内钉治疗,PFNA-Ⅱ组采用PFNA-Ⅱ治疗。对比两组术中及术后相关指标、并发症发生情况、手术前后的髋关节功能及生活质量变化。结果:INTERTAN组术后下床活动时间、术后住院时间、早期负重时间、骨折愈合时间均优于PFNA-Ⅱ组,手术时间长于PFNA-Ⅱ组,术中出血量多于PFNA-Ⅱ组,差异有统计学意义(P<0.05)。INTERTAN组并发症发生率低于PFNA-Ⅱ组,差异有统计学意义(P<0.05)。术前,两组髋关节功能、生活质量比较,差异无统计学意义(P>0.05);术后1个月、3个月,INTERTAN组髋关节功能、生活质量均高于PFNA-Ⅱ组,差异有统计学意义(P<0.05)。结论:对于老年股骨粗隆间骨折患者而言,对其实施INTERTAN髓内钉治疗有利于促进患者的术后恢复,降低并发症的发生风险,改善其髋关节功能及生活质量。

混凝土Ⅱ型断裂的FCM和断裂能

本文讨论了混凝土Ⅱ型断裂的机理,并给出了一个产生Ⅱ型断裂的充分条件.从而,提出了Ⅱ型虚拟裂纹模型(FCM).并据此用有限元计算了属于Ⅱ型的剪切断裂能和压剪断裂能.在用刚性加载架对混凝土试样测得剪切荷载-切口相对位移全曲线的基础上,获得了剪切断裂能和压剪断裂能的试验值,它与电算值相当接近.试验结果表明,混凝土Ⅱ型断裂能约为Ⅰ型断裂能的20倍.